The present invention relates to a biopsy instrument and an apparatus for collecting tissue samples or the like from humans or animals, in particular by excising a segment from a tissue.
In modern medicine, biopsy, i.e., the removal of material from a living human or animal body for examination by various methods such as microscopy, is carried out on a routine basis. Typically, such a procedure is used for diagnosis of malignant and pre-malignant cell transformations, which indicate the presence of cancerous or pre-cancerous tumors.
Routine techniques in which entire tissue segments are removed for histologic examination, known as core biopsy, make use of various kinds of hollow needle-like biopsy instruments. These instruments have canulae with a sharp front edge or a notched stylet for cutting into the tissue during insertion into the selected body area. The tissue portion that is to be removed as a biopsy sample is received in the cylindrical bore of the canula. Upon withdrawal of the biopsy instrument from the body the sample is retained in the cylindrical bore by mechanical or suction means and is separated from the main tissue body during the withdrawal process. The removed samples typically have a generally oblong cylindrical shape, or a longitudinal half-cylindrical shape.
The quality, e.g., width, length and amount of crushed cells, of biopsy samples for cytologic or histologic examination is an important factor that affects the examination result. Tissue biopsy samples should mirror the structure of live tissue as closely as possible. Therefore, strains on the samples during excision, severing from the tissue, and removal from the canula should be avoided.
Other important factors are the precision with which the tissue area selected for biopsy can be targeted by the biopsy instrument, the ease with which the biopsy instrument can be manipulated, the trauma that is caused to the patient by the procedure, and the cost of the biopsy instrument.
Patient trauma is minimized by minimizing transmission of kinetic energy by means of the lowest possible friction to surrounding tissue and the smallest possible moving mass/area during the biopsy needle stroke, and by keeping the portion of the biopsy instrument that is inserted into the patient's body as small as possible for a given volume of biopsy sample. Targeting is facilitated by modern tissue imaging methods, such as by ultrasound. Ease and, thus, reproducibility of manipulation is facilitated by automation.
U.S. Pat. No. 5,282,476 discloses an automated core biopsy device in which the canula is provided over a stylet that directs the canula to the biopsy site. After insertion, the canula is urged past the stylet to collect the sample. Suction means are employed for sample retention. However, this biopsy device is of rather complex design because of the suction means and requires substantial manipulating skills. In the hands of an untrained user, the device may yield uncertain results.
Automated core biopsy devices (ACBD) using sample retention means other than suction are known in the art. A combination of the so-called "True Cut" needle with an ACBD is disclosed in U.S. Pat. No. 4,699,154. The "True Cut" needle includes a canula with a sharp front edge and enclosing a cylindrical stylet that has a semicylindrical recessed portion near the point. Insertion of the stylet into tissue (by spring action) is followed by sliding the canula over the stylet, thus cutting and trapping a semicylindrical portion of tissue in the recessed portion of the stylet. The "True Cut" needle has a substantial drawback in that it can extract samples having half of the canula volume only, and also compromises tissue sample quality by forcing the stylet through the sample area.
Another biopsy instrument incorporating a "True Cut"-type needle is disclosed in Reissued U.S. Pat. No. Re. 34,056. One end portion of the needle assembly of this biopsy instrument is contained in a housing. Compressed springs in the housing expand to urge consecutively the needles away from the housing during the sampling of tissue.
Other needle types that use the full volume of the canula or of canula-like devices are known. For instance, U.S. Pat. Nos. 4,177,797, 4,781,202, and 4,785,826. They are, however, not suited for incorporation in an ACBD and/or have other drawbacks.